Velopharyngeal portal insufficiency

The velopharyngeal portal is a three-dimensional structure. Nasal endoscopy provides a good view, but it is limited to one imaging plane; it does not provide information regarding the vertical extent of the lateral pharyngeal wall motion, the length and thickness of the soft palate, the extent of palatopharyngeal contact, and the relationship of Passavants ridge to the palate. Radiographically, three imaging planes can be obtained: a lateral view, showing the elevation and posterior movement of the soft palate; a frontal view showing the medial movement of the lateral pharyngeal walls, and a base view showing the sphincteric activity of the portal.

The most refined method of assessing velopharyngeal portal insufficiency is videofluoroscopy, allowing simultaneous recording of speech and demonstration of roentgen images of the portal in motion. For example, in a normal situation the timing of the palatal movement relative to speech is approximately coincident (palatal movements are initiated slightly before speech is heard). Palatal movement may be slow, while in other patients a staccato, discontinuous movement is seen. Such abnormalities can be observed on videofluoroscopic examinations.

The lateral view allows appreciation of the length and configuration of the velum, location and height of the velar eminence, and the region of contact or closest approximation between the velum and posterior pharyngeal wall during phonation (Fig.1). Anterior motion of the posterior pharyngeal wall can be observed as a compensatory mechanism for velar insufficiency: this can be broad or localized (Passavants ridge). If adenoids are enlarged, their effects on palatal or tongue motion can be assessed (Fig.2).

The frontal view is best for delineating the movements of the lateral pharyngeal walls during phonation. These lateral walls can be hard to visualize, making a good coating with contrast medium desirable. Besides observing the horizontal direction of the maximum pharyngeal wall movement during speech, one can also study the symmetry and the vertical length of the moving wall segments (Fig.3). Sometimes the lateral walls show an asymmetrical position at rest, the more lateral wall possibly not reaching as close to the midline as the opposite one; sometimes symmetrically positioned lateral walls at rest show asymmetrical medial movement during phonation. Such abnormalities can be the cause of velopharyngeal portal insufficiency.

The basal view enables one to see the combined movements of the palate and the pharyngeal walls, creating a sphincteric narrowing or closure of the velopharyngeal portal. For this view, it is necessary to traverse the portal plane perpendicularly with the X-ray beam.

RH